Dynamic behaviors of rockslides subjected to brittle failure of locked segments

Locked segments are recognized as a critical role that controls the stability of rock slopes but remain an unclear and challenging problem with respect to their role incorporated into the failure mechanism.In order to study the effect of the locked segments on the initial failure process of rockslides,thirty-six groups of locked segment specimens with three different lithologies were prepared,direct shear tests were carried out to obtain the accelerations caused by brittle failure of the locked segment specimens.Experiment results showed that the maximum accelerations caused by the brittle failure of locked segment specimens was 2.91 g in the horizontal direction,and 3.18 g in the vertical direction.We took the Wangjiayan rockslide in 2008 Wenchuan earthquake as an example,the critical balance condition of the sliding mass under combined effect of gravity and accelerations induced by brittle failure of locked segment was analyzed,which indicated that the initial failure process of the Wangjiayan rockslides was notably influenced by the existence of the locked segment.The departure acceleration and direction of the Wangjiayan rockslide were proposed.The study results can provide a new insight into the understanding of the initial failure mechanism of rockslides with locked segments.

Analysis of nonlinear vibration for symmetric angle-ply laminated viscoelastic plates with damage

The behavior of nonlinear vibration for symmetric angle-ply laminated plates including the material viscoelasticity and damage evolution is investigated. By employing the von Karman＇s nonlinear theory, strain energy equivalence principle and Boltzmann superposition principle, a set of governing equations of nonlinear integro-differential type are derived. By applying the finite difference method, Newmark method and iterative procedure, the governing equations are solved. The effects of loading amplitudes, exciting frequencies and different ply orientations on the critical time to failure initiation and nonlinear vibration amplitudes of the structures are discussed. Numerical results are presented for the different parameters and compared with the available data.

Hierarchical Classification of Factors Associated With Noninvasive Prenatal Testing Failures and Its Impact on Pregnancy Outcomes

Objective To conduct a hierarchical classification analysis of the nonreportable results of noninvasive prenatal testing in an attempt to reduce failure rates and provide pregnant women with accurate information to alleviate their anxiety.Methods In this study,30,039 singleton pregnancies who underwent noninvasive prenatal testing in a single center from May 2019 to April 2022 were collected,and 811 samples with initial noninvasive prenatal testing failure were retrospectively analyzed.Grouping was based on the reasons for initial test failure;tracking the noninvasive prenatal testing results and prenatal diagnosis results(if any)of the“z-scores in the gray area”group and analyzing the possible influencing factors of the“low fetal fraction”group in the pre-experimental and experimental period by using one-way analysis of variance,Mann-Whitney U test,andχ2 test;and tracking the pregnancy outcomes of the test failures samples to analyze the risk of perinatal complications and adverse pregnancy outcomes of the different types of test failures.Results None of the samples'initial inconclusive results because of z-scores in the gray area were found to have chromosomal aneuploidy.However,pregnancy complications(P=0.018)and a high likelihood of adverse pregnancy outcomes(P=0.048)may still occur.Maternal gestational age(P<0.001),body mass index(P<0.001),library concentration(P<0.001),and fetal gender(P<0.001)were considered to be the associated factors for the initial low fetal fraction results.This may be associated with pregnancy complications(P<0.001)and a high likelihood of adverse pregnancy outcomes(P=0.034).The body mass index(P=0.015)and time between draws(P=0.001)were associated with the second test’s success.The incidence of low fetal fraction samples was more frequent with blood collection tubes of the G type than with the K type(P<0.001).Conclusion Initial inconclusive results because of z-scores in the gray area did not imply an increased risk of aneuploidy,but vigilance is needed for an increased risk of pregnancy complications and adverse pregnancy outcomes.Because of the low fetal fraction,the initial absence of results may be related to the assay method,as well as the effect of blood collection tubes and the need to be alert to the risk of pregnancy complications and adverse pregnancy outcomes.